Thermionic switching system



July 9, 1935. A. M L. NICOLSON 2,007,809

- THERMIONIC SWITCHING SYSTEM Filed. on; 4, 1950 2 Sheets-Sheet 2 I l INVENTOR Q Alexander 'M-Zean Mcolmz'z B UJ/KMW' ATTORNEY- Patented July 9, 1935 UNlTED STATES PATENT OFFICE Alexander McLean Nicolson, New York, N. Y., assignor to Communications Patents,'Inc., New York, N. Y a corporation of Delaware Application October 4, 1930,,Ser ial No. 486,336 11 Claims. (01. 2509) This invention relates to a method of and means for transmitting electrical signals and particularly to a system for transmitting a plurality of signals over a single pair of conductors or carrier channel.

An object of this invention is to transmit intelligence in the form of electrical signals with a minimum of equipment.

Another object of the invention is to transmit 2.

tion with a minimum frequency band width.

A still further object of the invention is to provide thermionic switching circuits at transmitter and receiver stations and to maintain the switch;

ing circuits in synchronism. a a

In systems in which carrier waves are used as the transmitting medium between two stations, a single pair of conductors may transmit a plurality of independent signals without interference between signals. However, a large frequency band is required to transmit these signals simultaneously since each channel requires a definite carrier frequency which must be separated from its adjacent frequency channels by a sufiicient frequency band to prevent cross-talk and other interferences caused by the higher order of modulation frequencies.

The present invention contemplates using one carrier frequency for the entire number of channels over a single pair of conductors. These channels may transmit sound, picture, or telegraph signals. The division or the separation of thesignals is a function of time instead of frequency, that is, the signals are divide-d into small time increments each signal being transmitted at a certain time epoch. These epochs occur at a sufficiently rapid rate to provide satisfactory continuity of each signal. The fundamental principles of this invention are disclosed in my co- In the present system the serial switching is accomplished by oscillators, each of which control nels and so on for any further number of chan- 55 nels; The master oscillator actuat es the two secplurality of electrical signals from station to sta' pending application S. N. 460,806, filed June 13,

ondary oscillators alternately which means that allsubsequent circuits of either secondary are made-inoperative during one-half cycle of the master oscillator. As each succeeding oscillator completes one cycle during its operative period, the'final control circuits'will be actuated in serial orderuntil they are made inoperative by the master oscillator. Each oscillator, therefore, acts as a facilitator and suppressor controlling either an oscillator or a transmission channel. It is obvious from the above statements that each subsequent oscillator is oscillating at twice the frequency of its immediate predecessor and is self oscillatory so that when the control oscillator is passing through its positive half cycle, the secondary oscillators will operate freely.

The invention will be more fully understood from the following description taken in conjunction with the accompanying drawings in which:

Fig. 1 shows a schematicdiagram of the transmitter arrangement of the system in accordance with the invention,

Fig. 2 shows a receiving circuit of the same system, and

Fig.- 3 is a diagram of the oscillating frequencies ineach oscillator.

Referring more specifically to Fig. 1, eight channels for the transmission of electrical signals are shown numbered from I to 8. The immediate translators from sound or othersources to electrical vibrations are shown as microphones in the inputs of amplifiers or control circuits Ito H- inclusive except channel 6 whichhas atelevision' source of signals- These circuitsmay be .ordinary amplifiers having transformers It to 26 inclusive in their input or grid circuits. The outputs .of-each of the individual circuits are shown connected in series through output transformers 28 to 35 inclusive and fed into an amplifier 3! which is connected to a transmitter system 38. The transmitter output may be broadcast or" transmitted over an antenna system 39 or over a wire circuit 40. The outputs from the individual systems H! to ll'inclusive may also be connected in parallel to the amplifier 3! but is shown in series as the preferred arrangement.

Referring to the control circuits for the transmitting channels -I to 8 inclusive, there is a master oscillator 42 of any well known type which preferably should be crystal controlled to give a more uniform frequency output. The output of this oscillator is connected through a transformer 43 to oscillators 44 and 45 of the same type as oscillater 42. Oscillators M and 45 are in turn coupled through-their output transformers 49 and 1 50 to oscillators 52 to 55 inclusive through respective transformers 51 to 60 inclusive. All of these oscillators may be of a type similar to master oscillator 42. The connection between each pair of oscillators and its preceding control oscillator is such that during one complete cycle of the control oscillator it alternately actuates the controlled oscillator, that is, each oscillator is made active and inactive during one cycle of the control oscillator. To perform this function in a particu larly eflicient manner the wave shape should be. slightly fiat topped which may be accomplished by any method well known in the art.

The four oscillators 52-55 inclusive of the embodiment disclosed control the eight channels above described through their respective output transformers 62 to 65 inclusive. For instance oscillator 52 is connected to channels I' and 2 through the transformers I9 and 20 respectively in the input circuit of amplifiers I0 and II. Now during one complete cycle of the oscillator 52 transmission may occur through each circuit alternately and during the transmission period of either channel, the other is suppressed. The frequency, or time epoch, at which these circuits are made inoperative depends upon the frequency of the master oscillator 42 and its subsidiary oscillators.

Assuming that the frequency of the master oscillator is kilocycles, the frequency of oscillators 44 and 45 is then 200 kilocycles, and the frequency of oscillators 52 and 55 inclusive is 400 kilocycles. The frequency of operation, therefore, of the circuits ID to I! inclusive, or channels I to 8 inclusive, is at therate of 800 kilocyclesper second. In other Words, transmission will take place through each channel during l/ 800,000 of a second. In the present system, therefore, the time epoch will be l/800,000 of a second for each channel, and transmission for all eight channels will take place in l/ 100,000 of a second.

Each oscillator will begin its oscillation in the proper time sequence since they are made operative simultaneously by a current increase at the commencement of the positive half-cycle of the master oscillator. In the master oscillator output circuit is shown a third winding 68 of the transformer 43 which is connected to the inputrof the transmitter 38. This circuit impresses upon the input of the transmitter for transmission to the receiving system the frequency of the master oscillator which I have assumed as 100 kilocycles. This frequency will not interfere with the frequency obtained from the oscillator 52 to 55 inclusive as it is sufficiently low to be easily separable.

Referring now to Fig. 2 which illustrates a receiving system in accordance with theinvention, an antenna ID, or wire circuit II, feeds a receiver 12, the output of which after amplification by an amplifier 13, is impressed upon input transformers I4 to BI inclusive of control circuits 82 to 89 inclusive. This input circuit is shown in series but may be in parallel similarly to the output circuit of the transmitter channels III to H inclusive. The outputs of the receiver circuits 82 to 88 inclusive are impressed upon receivers of different types such as the head phones shown in receiving channels I, 2, I and 8, or loudspeakers as shown in channels 3, 4, and 5, or in. television apparatus as shown in channel 6.

For the control circuits of the receiving channels there is a pyramidal series of oscillators 9| to 91 inclusive arranged identically as oscillators 42, 44,45, 52, 53, 54, and 55, of the transmitter circuit of Fig. 1. Each oscillator corresponds to its counterpart at the transmitter and oscillates at the same frequency as its counterpart. Thus, master oscillator 9| oscillates at 100 kilocycles, oscillators 32 and 93 oscillate at 200 kilocycles, and oscillators 94 to 91 inclusive oscillate at 100 kilocycles.

In the output of the amplifier 13, a circuit 99 is shown connecting a filter I00 to the input of master oscillator 9| over conductors IOI. Althrough master oscillator 9| is self-oscillatory, it is held in step with the transmitting oscillator 42 by the 100 kilocycle frequency which is filtered from the output amplifier I3 and impressed upon its input and any tendency of the oscillator BI to deviate from its proper frequency will be checked and prevented. Furthermore, should the oscillator 42 tend to vary, the varying frequency impressed on oscillator 9| will shift its local frequency to conform therewith since the variation will-necessarily be small. This pulling into step of oscillators is well known in the art and is adaptable in this system for keeping the two oscillators in synchronism. A filter I02 may be used to prevent the 100 kilocycle piloting frequency from reaching the control circuits, but since this frequency is above audibility this filter is not required.

Referring to the output circuits, these circuits will be facilitated and suppressed in the exact order of the transmitter circuits I to 8 so that during the time epoch when the increment of a certain channel is being received the receiving circuit for that channel is operative to pass on the signals to the receiving device.

The manner in which this transmission occurs is graphically represented in Fig. 3 wherein the master oscillator frequency is shown as a, the secondary oscillator frequency as b, and the sub-oscillator frequency as c, The oscillator 42 oscillating at a frequency will permit oscillator 44, during the first one-half cycle to make one complete cycle as shown at b. The positive one-half of the b cycle then permits oscillator 52 to make one complete cycle as 0 cycle. The complete 0 cycle of oscillator 52 facilitates channel I and the channel 2 alternatively, transmitting channel I being suppressed while channel 2 is facilitated and vice versa. The 2) cycle then renders oscillator 52 inoperative and oscillator 53 operative, oscillator 53 in turn operating and suppressing channel 3 and channel 4 in that order. At the end of this time epoch master oscillator 42 suppresses oscillator 44 and consequently oscillators 52 and 53 and the four channels. Simultaneously oscillator 45 is facilitated operating channels 5, 6, I, and 8 in that order in the same manner as oscillator 44 facilitated channels I to 4 inclusive. If sixteen channels are desired, the provision of eight intermediate oscillators between the control circuits and the four final oscillators above disclosed will bring about the proper result.

Furthermore the receiving stations may be spatially separated and correspondingly selective to transmitter stations I-8 inclusive. In fact said receiving stations may represent different broadcast receiver stations for simultaneous, non-interfering receptions from transmitter stations I-8 inclusive. 7

It is to be understood that there are other modiflcations and applications of the pyramidal oscillator switching circuits adaptable to other transmission systems. such as television and telegraph communication, and the invention is to be limited only by the scope of the appended claims.

What is claimed is:

1. In an electrical transmission system, a plurality of means for'pro-ducing signals to be transmitted, a common transmission circuit for all of said signals, a plurality of oscillators each of which control the transmission of a group of said plurality of signal producing means in a serial order, and a second plurality of oscillators having their outputs connected to the inputs of said first plurality of oscillators for controlling the operation of said oscillators, the frequency of one plurality of oscillators differing from the frequency of the other plurality of oscillators by an even harmonic.

2. In an electrical transmission system, a plurality of means for producing signals to be transmitted, a common transmission medium for said signals, and a plurality of oscillators each of which controls the transmission of a group of said plurality of signal producing means in a serial order, and an oscillator having its output connected to the inputs of said plurality of oscillators for controlling said plurality of oscillators, said plurality of oscillators operating at the first even harmonic of said control oscillator.

3. In an electrical transmission system, a plurality of means for producing signals to be transmitted, a common transmission medium for said signals, a plurality of oscillators each of which controls the transmission of a group of said plurality of signal producing means in a serial order, a second group of oscillators controlling said last mentioned oscillators, the outputs of which are connected to said plurality of oscillators, and an oscillator for controlling the period of operation of said second, group of oscillators, the frequency difference between said groups of oscillators and said control oscillator being even harmonics.

4. In an electrical transmission system, a plurality of means for producing signals to be transmitted, a common transmission medium for said signals, a receiving device for each of said signals, respectively, a plurality of oscillators directly connected to said plurality of signaling means for operating said means in a serial order, a second plurality of oscillators having their outputs connected to the inputs of said first plurality of oscillators, a group of oscillators corresponding to said first plurality directly connected to said receiving devices for operating said devices in a serial order corresponding to the operating order of said signaling means, a second group of oscillators having their outputs connected to the inputs of said first group of oscillators, the variation in frequency of oscillations between said groups of oscillators being an even harmonic, and means for maintaining said oscillators in synchronism.

5. In an electrical transmission system, a plurality of means for producing signals to be transmitted, a plurality of receiving devices for receiving said signals, respectively, a common transmission medium between the said signaling means and said receiving devices, a plurality of oscillators directly connected to' said signal producing means'for operating said means in a serial order, a second plurality of oscillators having their output circuits connected to the input circuits of said first plurality of oscillators, a group of oscillators directly connected to said receiving devicesfor operating said devices in a corresponding serial order, a second group of oscillators having their output circuits connected to the input circuits of said first group of oscillators, the variation in frequency between said groups of oscillators being an even harmonic, and means for maintaining synchronism between corresponding oscillators.

6. In an electrical transmission system, a plurality of means for producing signals to be transmitted, a common transmission medium for all of said signals, output circuits directly connected to each of said signaling means, oscillators directly connected with the said output circuits, a second oscillator having its output circuit connected to the input circuits of said oscillators, the frequency of said oscillators differing by an even harmonic from that of said second oscillator and means for controlling the period of operation of said last mentioned oscillator;

7. In a thermionic switching device, a master oscillator, secondary oscillators having input circuits connected to the output of said master oscillator, subsidiary oscillators having their input circuits connected to the output of said secondary oscillators in the same manner as the secondary oscillators are connected to the output of said master oscillator, said groups of oscillators differing in frequency by even harmonics, a plurality of means for producing signals to be transmitted, and means for connecting said subsidiary oscillators with said signal producing means, said last mentioned means being made operative in serial order during? oscillation of said master os cillator.

8. A thermionic switching device in accordance with claim 7, in which the master oscillator is associated with the output of said transmission channels for transmitting the frequency of said master oscillator.

9. A method of controlling the time sequence of operation of a plurality of groups of oscillators comprising interconnecting the outputs of a smaller number of oscillators with the inputs of a larger number of oscillators, alternate oscillators of said larger number being connected in an opposite phase arrangement from one of said smaller number of oscillators and tuning the larger group of oscillators to an even harmonic of the frequency of said smaller group of said oscillators.

10. In a multi-channel transmission system, a plurality of means for producing signals to be transmitted, an amplifier for said signals directly connected to said signaling means, a plurality of oscillators directly connected to said amplifiers for operating said amplifiers in a serial order, and means for controlling the operation of said oscillators from a master control oscillator con nected to the inputs of said plurality of oscillators, the frequency of which is an even sub-harmonic of the plurality of said oscillators.

11. In a multi-channel transmission system, a plurality of signal producing means, individual amplifiers for each of said means, a common output circuit for all of said amplifiers for transmitting said signals thereover, a plurality of oscillators operating at mutually exclusive intervals, said oscillators being directly connected to said amplifiers and operating said amplifiers in a serial order, and an oscillator connected to the inputs of said plurality of oscillators and operating at, an even sub-harmonic frequency below the frequency of said plurality of oscillators for controlling the period of operation of said oscillators.

ALEXANDER MCLEAN N ICOLSON. 

